1. Field of the Invention
The present invention concerns a process for the production of lignolytical enzymes by means of Phanerochaete chrysosporium.
2. Description of the Related Art
During the last ten years, it has been tried repeatedly to use the pocket rot fungus Phanerochaete chrysosporium for the production of lignolytical enzymes at industrial level. For example, there are experiments in the stirring fermenter (H. Janshekar and A. Fiechter, Journal of Biotechnology, 8 (1988), 97-112). However, these experiments were not very successful, because the pellets formed by Phanerochaete chrysosporium in the stirring fermenter were shattered time and again. However, since Phanerochaete chrysosporium only produces enzymes if it is present in pellet or immobilised form, optimal enzyme production cannot be realised in the stirring fermenter.
Moreover, biotechnology has developed reactors especially designed for sensitive cells. For example, a so-called "vibromixer" has been developed which is even suitable for sensitive animal and plant cells (Einsele, Finn, Samhaber: Mikrobiologische und biochemische Verfahrenstechnik (Microbiological and Biochemical Technology), Weinheim 1985, p. 150; Einsele: Chem.Ing.Tech. 45 (1973), 1368; Rehm: Chem.Ing.Tech. 42 (1970), 583). The effect of the vibromixer is based on the Bernoulli effect. Instead of the stirrer, a horizontal plate attached to a vertical shaft is positioned inside the vessel, said plate having drilled holes tapering downwards. It is moved up and down by means of the shaft. This movement causes pressure differences in the drilled holes, because the liquid in the openings flows back from the large to the small diameter. Even though the cells are moved well that way, there is practically no damage. However, such a vibromixer has the disadvantage that it still is not gentle enough for the sensitive pellets of Phanerochaete chrysosporium. Besides, such vibromixers cannot be used at a commercial scale to date.
Finally, glass vessels moved by mechanical shakers are also suitable for the formation of pellets of microorganisms (H.J. Rehm: Einfuhrung in die industrielle Mikrobiologie (Introduction into Industrial Microbiology), Berlin-Heidelberg-New York 1971). For this purpose, the vessels (mostly bottles or Erlenmeyer flasks) are clamped into the mechanical shakers in multi-stage tiers. As a result of the shaking of the vessels, air is mixed into the solution from the surface. For shaking, one uses amplitude, rotation and vibration machines which usually have variable speeds. These vessels may have planar bulges, the so-called baffle plates. The disadvantage of these systems is that they are only suitable at laboratory scale. For large-scale commercial application, thousands of bottles or Erlenmeyer flasks would be necessary, so that the use of such devices is not reasonable.
In order to solve the above-mentioned problems of using stirring reactors, scientists have increasingly tried working with immobilised cells (S. Linka, Journal of Biotechnology, 8 (1988), 163-170; H. Willershausen, A. Jager, H. Graf, Journal of Biotechnology, 6 (1987), 239-243; Y. Linko, M. Leisola, N. Lindholm, J. Troller, P. Linko, A. Fiechter, Journal of Biotechnology 4 (1986), 283-291). However, these processes also failed at large scale. As a rule, they were no longer practicable at a fermenter volume of more than 40 l. Essentially, the reason for this can be found in the fact that Phanerochaete chrysosporium in pellet form has an optimal surface and thus produces enzymes best while in this state.